Optimal design of the transmission-way of mechanical stress throughthe interface between a joint prosthesis and bone tissue together with the criterion formulation for the assessment of the fixation method

超高分子量聚乙烯（UHMWPE）的失效准则应在关节假体强度设计中明确。在本研究中，我们在与全膝关节假体相似的条件下对UHMWPE接骨板进行了压缩试验和有限元（FE）分析，并讨论了失效标准。这些厚度的范围为2 mm至8 mm。在37 ℃下在充满盐水溶液的浴中进行使用加载机的压缩测试。使用直径为50 mm的金属球作为压头。在2 mm/min的十字头速度下施加6 kN的载荷。在测试之后，将流动压力计算为压痕面积与最大负载的比率。通过边缘位移估计接骨板的变形。此外，在虚拟模型上使用与 关于我们 对于常规UHMWPE，流动压力的值被测量为平均值32.8MPa，SD 2.3MPa，对于交联UHMWPE，流动压力的值被测量为平均值37.3MPa，SD 0.9MPa。UHMWPE接骨板的位移随着接骨板厚度的减小而增加。有限元分析估算的位移与实验结果相似。随着位移的增加，UHMWPE板的剪切应变也随之增加。结论：关节假体的失效标准不仅要考虑UHMWPE衬垫的应力，还要考虑其应变，植入物压配固定后骨组织中的应力必须保持不变。残余应力必然引起种植体周围的生物学反应。由于残余应力是静态的，与生理力学条件不同，其影响尚未得到充分的讨论。在本研究中，我们开发了一种利用超弹性骨针在大鼠股骨中构造静态应力场的方法。结果发现，在6周的固定载荷作用下，骨髓内的骨针在股骨边缘出现了骨肥大。少

Failure criteria of ultra-high molecular weight polyethylene (UHMWPE) should be clarified for the strength design of joint prostheses. In the present study, we performed compression tests of UHMWPE plates together with finite element (FE) analysis under conditions similar to those within a total knee prosthesis and discuss the failure criteria.Flat plates made of conventional or cross linked UHMWPE were molded as test pieces. Those thicknesses were ranging from 2 mm to 8 mm. The compression test using a loading machine was performed in a bath filled with saline solution at 37 degrees centigrade. A metallic sphere 50 mm in diameter was used for the indenter. The load was applied to 6 kN under a crosshead speed of 2 mm per minute. Flow pressure was calculated after the test as a ratio of the impressio area and the maximum load. Deformation of the plate was estimated by displacement at the edge. Additionally, the FE analysis was performed on a virtual model using the same conditions as in … More the experiments.The values of the flow pressure were measured as a mean of 32.8 MPa, SD 2.3 MPa for conventional UHMWPE, and as a mean of 37.3 MPa, SD 0.9 MPa for cross-linked UHMWPE. The displacement of the UHMWPE plate increased with decreasing thickness of the plate. The displacement estimated by FE analysis was similar to that of theexperimental findings. Furthermore, shear strain in the UHMWPE plate of FE model increased with the displacement. It was concluded that the failure criteria of joint prostheses must be presented by not only the stress but also the strain in a UHMWPE insert.Stress in bone tissue must be remained after the press-fit-fixation of a implant. The residual stress must bring on the biological response around the implant. The effect has not been sufficiently discussed, yet, because the residual stress is stationary and unlike the physiological mechanical conditions.In the present study, we developed a method to configure stationary stress field in a rat femur using a pin with the hyper elasticity. As the results, it was observed that bone hypertrophy emerged at the fringe of the femur under six weeks stationary load from the pin inside bone marrow. Less